Resins (polymers) having a cyclic structure in the main chain are excellent in durability, especially heat resistance, and thus they are useful materials used in various fields such as engineering plastics, optical materials, and resist materials. Particularly, in recent years, various resin compositions such as radical curable resin compositions, colorant-dispersed compositions, and photosensitive resin compositions are produced from the above resins. Applications of these resin compositions for coating materials, high-performance inks, and resist materials have been considered.
Curable resin compositions are used in various industrial fields. In particular, a radical curable resin composition comprising a radical polymerizable monomer and a binder resin is excellent in characteristics such as a curing rate, durability of a chemical bond to be formed, and cost efficiency. Thus, it is used for a wide range of applications, such as coating materials, adhesives, sealants, pressure-sensitive adhesives, paints, inks, resists, dental materials, lenses, and molding materials.
On the other hand, alkali-soluble resins are used as materials in various industrial fields, from materials for civil engineering and construction to materials for electronic information. One main application thereof is an alkali-developable resist.
An alkali-developable resist (hereinafter, also referred to simply as a resist) is generally a resin composition comprising an alkali-soluble resin, a curable component, a photo initiator for curing the curable component, and a solvent. This resist is an industrial material indispensable and useful to photolithography, and examples thereof include various resists according to their applications, such as solder resists, etching resists, interlayer insulating materials, plating resists, and resists for color filters. Among these, resists for color filters are ones of the resists which are required to have the highest and various characteristics.
A color filter is a main component constituting a color liquid crystal display panel and a color image pick-up device. It has a fine colored layer for separating colors, and such a structure enables a liquid crystal panel and an image pick-up device to display colored images. One main method for forming a colored layer is photolithography using an alkali-developable photosensitive resin composition (hereinafter, also referred to as a color resist) containing an alkali-soluble resin, a radical polymerizable monomer, a photo initiator, a colorant as a coloring component, and a dispersant for the colorant. Production processes of a color filter or a liquid crystal display panel include many steps where heat higher than 200° C. is applied. Thus, the colored layer of a color filter is required to be resistant to such thermal history. Further, recently, color filters are much more required to have higher color purity for improved display quality and imaging quality, and the colorant concentration in the color resist tends to be high. However, high colorant concentration in the color resist causes reduction in colorant-dispersion stability and image-forming properties of the color resist (e.g. coatability, curability, development residues, developing time, edge shape, and resolubility after drying). If the quantity of a dispersant increases for ensuring the dispersion stability of the colorant, the quantities of the radical polymerizable monomer and the alkali-soluble resin are to be reduced, and thus the image-forming properties of the color resist tend to be deteriorated and heat resistance (e.g. resistance to heat decomposition and heat-resistant transparency) tends to greatly decrease.
In alkali-developable resists such as a resist for color filters, the alkali-soluble resin is a component which imparts film formability and solubility into a developing agent to a resist, that is, which makes resists resist. It is also called a binder resin for its role. Further, the alkali-soluble resin is a component which controls various properties such as curability, adhesiveness, heat resistance, resolubility after drying, and heat resistance. Thus, in order to solve problems in resists, an appropriate binder resin is used for solving the problems in many cases.
Many methods for improving a binder resin are proposed in order to solve the aforementioned problems in the resist for color filters. One example thereof is a method in which a resin which has a cyclic structure in its main chain and which is known to have excellent durability, especially heat resistance is used as a binder resin (for example, see Patent Document 1 and Patent Document 2). In particular, the resin disclosed in Patent Document 1 is considered to provide a color resist excellent in properties such as curability, solubility in a solvent, developability, dispersibility, and adhesiveness, and to be effective in solving the aforementioned problems.
As mentioned above, a resin having a cyclic structure in its main chain is excellent in durability and heat resistance, and is used for various applications. Such a resin may be produced by coupling monomers each having a cyclic structure with each other by a polycondensation mechanism or an addition polymerization mechanism, and thereby incorporating the cyclic structures of the monomers into the main chain. Examples of a resin having a cyclic structure in its main chain produced by the polycondensation mechanism include polycarbonates, polyimides, and polyphenylene sulfides. These resins have very high heat resistance and are mainly used for engineering plastics. However, these resins are produced under very hard conditions such as those with high temperature and high pressure, or those generating hydrochloric acid. Thus, it is disadvantageously difficult to control performance suitable for its application and to impart various characteristics.
In contrast, the addition polymerization mechanism allows easy control of the molecular weight and copolymerization with various vinyl monomers under mild conditions. Thus, this mechanism enables easy control of performance suitable for its application and easy impartation of various characteristics in addition to heat resistance. Therefore, the mechanism is used for synthesizing resins used for applications requiring high and various characteristics, such as optical materials and resist materials. Examples of a resin having a cyclic structure in its main chain produced by the addition polymerization mechanism include cycloolefin polymers synthesized by coordination polymerization of cycloolefins and maleimide-based polymers synthesized by radical polymerization of N-substituted maleimides.
On the other hand, the resin having a cyclic structure in its main chain may be synthesized by addition-polymerizing and simultaneously cyclizing monomers each having no cyclic structure. Examples of such a method include a method in which 1,6-dienes are polymerized by a radical polymerization mechanism to form a resin having a 5- or 6-membered ring in its main chain (for example, see Non-Patent Document 1, Non-Patent Document 2, and Non-Patent Document 3). The cyclic structure is formed upon polymerization in such a method. Thus, the method provides a novel synthesizing method different from the aforementioned polycondensation and addition polymerization in which monomers each having a cyclic structure are preliminarily prepared.
Patent Document 1: JP 2006-161035 A
Patent Document 2: JP 2003-201316 A
Non-Patent Document 1: Takashi Tsuda, and one other, “POLYMER” (Holland), 1994, vol. 35, pp. 3317-3328
Non-Patent Document 2: Rovert D. Thompson, and two others, “Macromolecules” (United States), 1992, vol. 25, pp. 6455-6459
Non-Patent Document 3: Michio Urushisaki, and four others, “Macromolecules” (United States), 1999, vol. 32, pp. 322-327